Optoelectronic devices used in modern optoelectronic and photonic applications generally include one or more of an emitter, an optical modulator, and a photodetector. For example, an emitter such as, but not limited to, a laser or a light emitting diode (LED) may be used to generate light, while an optical modulator may be employed to modulate one or both of an amplitude and a phase of light in various optoelectronic and photonic applications. Photodetectors such as, but not limited to, photodiodes, are often used to receive and detect light in modern optoelectronic and photonic applications, for example. In particular, semiconductor photodetectors often based on p-n and p-i-n semiconductor junctions (e.g., PN photodiodes, PIN photodiodes, etc.) and related photovoltaic devices are very common in modern photonic systems.
In general, semiconductor photodetectors provide high performance (e.g., high speed) with concomitant exceptionally good reliability at relatively low cost. For example, an avalanche photodiode (APD) may provide both conversion of incident light into a photocurrent and a ‘built-in’ first stage photocurrent gain through avalanche multiplication resulting in a relatively high sensitivity in many photodetection applications.
Unfortunately, while semiconductor photodetectors generally enjoy wide applicability, usefulness of a given semiconductor in certain instances may be limited by a band gap of the semiconductor. In particular, it may be difficult to realize a desired absorption spectrum or photo-response for an arbitrary semiconductor in a specific photodetector application. For example, an ‘all-silicon’ photodetector (e.g., APD) may be attractive in terms of manufacturing cost and ease of integration with other circuitry (e.g., with complimentary metal-oxide semiconductor circuitry). However, silicon has a relatively large band gap that may effectively preclude its use in certain photodetection applications where an optical wavelength (or photon energy) is not well matched to such a large band gap (e.g., various telecommunications applications). In such instances, it is common to employ other semiconductors with narrower band gaps either instead of silicon (e.g., indium phosphide, indium gallium arsenide, etc.) or in combination with silicon (e.g., germanium-silicon).
Certain examples have other features that are one of in addition to and in lieu of the features illustrated in the above-referenced figures. These and other features are detailed below with reference to the above-referenced figures.